## Chemistry: The Central Science (13th Edition)

$Ni$ has the same number of electrons as $Zn^{2+}$, but does not have the same electron configuration. No other neutral atoms have both the same number electrons and the same electron configurations with $Zn^{2+}$.
$Zn^{2+}$ A neutral $Zn$ atom has 30 electrons. Losing 2 electrons to become $Zn^{2+}$ cation, it now has 28 electrons. The neutral atom that has 28 electrons is $Ni$. The electron configuration of $Zn$ is $[Ar]3d^{10}4s^2$. Now we need to remove 2 electrons so that $Zn$ would become $Zn^{2+}$, and 2 electrons to be removed are 2 electrons that fill the $4s$ orbital (when electrons need to be removed to create ions, we would remove the electrons of the orbitals with the highest prinicipal quantum number, in the case, 4). Then, the electron configuration of $Zn^{2+}$ is $[Ar]3d^{10}$. Unfortunately, the electron configuration of $Ni$ is $[Ar]3d^84s^2$. So, the electron configurations are different.